It is well known to provide a polyhedral die in which when the die is thrown the probability of any of the faces facing upwards when the die come to rest is equal. U.S. Pat. No. B2-6,659,459 describes a die capable of being opened. However, an opening mechanism for the die comprises a button on the face to be opened first, which button destroys the symmetry of the die.
It could therefore be helpful to provide an openable die in which an object can be concealed and subsequently revealed to allow for novel and amusing games.